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अखिल भारतीय आयुर्विज्ञान संस्थान, नई दिल्ली
All India Institute Of Medical Sciences, New Delhi

Dr Ratna Sharma

Stress and Cognitive Electroimaging Lab

Given the fact that AIIMS accords priority to biomedical research, and given that I have received scientific training as a student in AIIMS and also as a Faculty member, I have always been fortunate to be in a strategic position, so as to contribute significantly in the research domain by conceptualizing and developing new projects, techniques and methods that have added value to both the existing knowledge domain and progressing new & innovative research. For the last 26 years I have been working in the field of neurophysiology. 

With funding from Department of Science and Technology, Government of India, Stress and Cognitive Electroimaging Lab was established in the Department of Physiology at AIIMS in 2011.

In the last 8-9 years we have attempted to make substantial contributions towards understanding the neural underpinnings of various cognitive domains, in healthy individuals as well as in neuropsychiatric and neurodegenerative disorders.

Quantitative EEG data of more than 380 healthy adults, 65 children, 55 elderly and 250 patients (including Parkinson’s & Alzheimer’s disease, mild cognitive impairment, Schizophrenia, Autism, Attention deficit Hyperactive disorder, Glaucoma and Addiction) across wide range of age group has been collected and analyzed during baseline and during testing of varied cognitive domains.

Various cognitive domains being studied range from perception, memory (verbal and picture), working memory, interference, attention (both auditory and visual) to emotions. This has enabled us to standardize the age related cognitive changes in either gender across cognitive domains.

Fundamental phenomena like changes due to stress, meditation, language, audio-visual integration, motor imagery and binocular rivalry have also been targeted as core areas for research. So far, the neural correlates in terms of networks activated, their neural sources and coherent activation compared to baseline conditions has been achieved using Quantitative EEG.

Quantitative EEG (QEEG) is the methodological analysis of EEG to derive the quantitative measures that reflect the underlying physiology and pathophysiology.

QEEG measures such as spectral power, coherence, EEG microstates, source localization, connectivity measures, causality measures and graph theory measures are being used in our laboratory to study the brain activity of patients and healthy controls.

One of the main strengths of our lab is dense array EEG acquisition using 128-channel EEG that provides greater precision and accuracy in localizing the brain sources of EEG activity across 6239 voxels that are correlated directly to structures revealed by MRI.

One of the notable contributions of the lab in understanding mental disorder is the identification of brain sources at left inferior parietal lobule and left temporal gyri for the shortened resting EEG microstate in Schizophrenia ( EEG microstates are the momentary spatial configuration of brain electric field at the scalp that reflect quasi-stable “functional microstates” caused by activity of different intracranial generators. Lab has also identified an EEG microstate in healthy individuals that predicts the outcome in a visuospatial working memory task in young adult subjects with increasing memory load (

We are in the process of publishing an important EEG biomarker based on brain source connectivity measures that has shown good sensitivity and specificity in distinguishing the Alzheimer’s disease, mild cognitive impairment and healthy aged controls. We are currently exploring graph theory to study the dynamics of brain networks by measuring the clustering coefficient, characteristic path length and small world coefficient. These graph theory measures would help us in identifying brain regions that function as hubs and nodes of the brain networks in health and disease states. Many complex real-world phenomena including EEG signals are characterized by nonlinear dynamics and the chaos theory. Therefore, we have plans to incorporate the non-linear dynamical measures of complexity and stability to quantify critical aspects of brain dynamics.

QEEG data of patients has been collected and analyzed using these analysis strategies. The Lab has collaboration with Department of Neurology, Psychiatry, Deaddiction Centre, Paediatric Neurology and Ophthalmology of AIIMS, New Delhi.

We aim to develop a platform for screening and profiling of patients with psychiatric and neurodegenerative disorders that can be used as a neural signature /biomarker in these disorders. This of utmost importance in conditions such as dementia, ADHD, Autism, Depression wherein there is no objective gold standard for diagnosis, which often leads to over/under diagnosis.

The research group includes One Professor (Prof Ratna Sharma) three Assistant Professors (Dr Simran Kaur, Dr Prashant Tayade, Dr Suriya Prakash), ten PhD, five MD, four MSc students and one ICMR RA. Research publications (published and under publication) includes international and national original articles, that have also been applauded by the institute (received AIIMS Excellency award 2017) and other forums (APPI awards) and other research grants from various funding agencies (DST, DBT, DHR, Ayush, AIIMS).

We aim to accelerate our research in both fundamental and clinical neurosciences. In addition to above aim, we plan to provide EEG as a preoperative tool for neurosurgery in order to map and localize the areas of important functions like language, movement, vision etc. in order to protect these functions during tumor resection.

Finally, could this research be the underlying basis for possibly augmenting mental capabilities of a healthy subject in the event of higher work load or stress or restoring mental and physical capabilities in disease. To make these possibilities a reality, we are working towards using EEG to direct computers/ machines. A study is being conducted to create a brain computer interface based on EEG data of motor imagery using machine learning algorithm and mu rhythm based feedback training for rehabilitation purposes.

  1. Thesis work competed as chief supervisor: 9 PhD, 5 MD, 1 MSc
  2. Thesis work being conducted as chief supervisor: 2 PhD, 2 MD
  3. Thesis work being conducted/ completed as co chief supervisor: 3 PhD, 5 MD, 3 MSc.
  4. Thesis work being conducted/ completed as co chief supervisor for other departments: 3 DM Pediatric Neurology & 1 DM Psychiatry (De-addiction)
  5. Post Doctoral students: 2 Research Associates


Full length publications: 51

Abstracts publication: 116 


Dr Ratna Sharma

Full length paper published: First author/ corresponding author in BOLD




  1. Samanchi R, Muthukrishnan SP, Dada T, Sihota R, Kaur S, Sharma R. Altered spontaneous cortical activity in mild glaucoma: A quantitative EEG study. Neuroscience Letters, Volume 759: 136036, , 2021,
  2. Gurja JPK, Muthukrishnan SP, Tripathi M, Sharma R. Reduced Resting State Cortical Alpha Connectivity Reflects Distinct Functional Brain Dysconnectivity in Alzheimer’s Disease and Mild Cognitive Impairment. Accepted in Brain connectivity, June 2021
  3. Zacharia, A.A., Ahuja, N., Kaur, S., Sharma R Frontal activation as a key for deciphering context congruity and valence during visual perception: An electrical neuroimaging study, 2021, Brain and cognition, 150: 105711. DOI:
  4. Gopal Chandra Janaa,*, Ratna Sharmab , Anupam Agrawala A 1D-CNN-Spectrogram Based Approach for Seizure Detection from EEG Signal from EEG Signal Procedia Computer Science 167 (2020) 403–412
  5. Anita Pal, Vinay Goyal, Madhuri Behari, Ratna Sharma. Study of EEG Microstates in Parkinson’s disease: A potential biomarker? Cognitive Neurodynamics, 2020, DOI: 10.1007/s11571-020-09643-0
  6. Anita Pal, Nishi Pegwal, Madhuri Behari, Ratna Sharma. High delta and gamma EEG power in resting state characterise dementia in Parkinson’s patients. Biomarkers in neuropsychiatrya. 2020 DOI: 10.1016/j.bionps.2020.100027
  7. Muthukrishnan, SP, Soni S, Sharma R. Cingulate oscillatory activity reflects the quality of memory representations in visuo-spatial working memory. Memory 2020; DOI: 10.1080/09658211.2020.1826525
  8. Kaur M, Sharma HB, Kaur S, Sharma R, Sharma R, Kapoor R, Deepak KK. Comparison of two formats of journal club for postgraduate students at two centers in developing critical appraisal skills. Adv Physiol Educ 44: 592–601, 2020; doi:10.1152/ad- van.00111.2019.
  9. Zacharia, A.A., Ahuja, N., Kaur, S., Mehta N, Sharma R. State-dependent perception and perceptual reversals during intermittent T binocular rivalry: An electrical neuroimaging study, Neuroscience Letters 736 (2020) 135252,
  10. Soni S, Muthukrishnan SP, Sood M, Kaur S, Sharma R. Altered parahippocampal gyrus activation and its connectivity with resting-state network areas in schizophrenia: An EEG study. Schizophr Res. 2020.
    doi: 10.1016/j.schres.2020.03.066
  11. Zacharia, A.A., Ahuja, N., Kaur, S., Mehta N, Sharma R. Does valence influence perceptual bias towards incongruence during binocular rivalry? Cogn Process (2020).
  12. Suriya Prakash Muthukrishnan, Sunaina Soni, Ratna Sharma. Brain networks communicate through theta oscillations to encode high load in a visuospatial working memory task: An EEG connectivity study. Brain Topography 2019;
  13. Srivastava A, Sharma R, Goyal V, Chaudhary S, Sood SK, Kumaran S.  Saccadic Eye Movements in Young-Onset Parkinson’s Disease - A BOLD fMRI Study Neuro-Opthalomology, 2019;
  14. Sunaina Soni, Suriya Prakash Muthukrishnan, Rupesh Samanchi, Mamta Sood, Simran Kaur, Ratna Sharma ‘Pre-trial and pre-response EEG microstates in schizophrenia: An endophenotypic marker’, Behavioural Brain Research, 2019, 371:
  15. Gurja JPK, Muthukrishnan SP, Tripathi M, Mehta N, Sharma R. Multi-domain Cognitive Testing: A Biomarker for Classifying the Cognitive Status of Mild Cognitive Impairment and Alzheimer’s Disease, Accepted for publication in the Neurology India 2019.
  16. Nishi Pegwal Anita Pal Ratna Sharma "Deactivation of default-mode network and early suppression of decision making areas during retrieval period by high arousing emotions improves performance in Verbal working memory task," Cognitive, Affective, and Behavioral Neuroscience,  2019, 19: 231-238,
  17. Chacko SG, P. Tayade, S. Kaur and R. Sharma, "Creation of a high resolution EEG based Brain Computer Interface for classifying motor imagery of daily life activities," 2019 7th International Winter Conference on Brain-Computer Interface (BCI), Gangwon, Korea (South), 2019, pp. 1-5. doi: 10.1109/IWW-BCI.2019.8737258
  18. Anita Pal Nishi Pegwal Madhuri Bihari Ratna Sharma `Is Dementia in Parkinson' disease related to chronic stress, anxiety and Depression?` Annals of Indian Academy of Neurology, 2019, DOI: 10.4103/aian.AIAN_341_18
  19. Anita Pal Nishi Pewal Simran Kaur Madhuri Bihari Ratna Sharma .Deficit in specific cognitive domains associated with dementia in Parkinson’s disease, Journal of Clinical Neuroscience, 2018, 57: 116-120.
  20. Batabyal T, Muthukrishnan SP, Sharma R, Tayade P, Kaur S. Neural substrates of emotional interference: A quantitative EEG study. Neurosci Lett. 685: 1-6. 2018. doi: 10.1016/j.neulet.2018.07.019.
  21. Sunaina Soni, Suriya Prakash Muthukrishnan, Mamta Sood, Simran Kaur, Nalin Mehta, Ratna Sharma. A novel method for assessing patients with Schizophrenia and their first-degree relatives by increasing cognitive load of visuo-spatial working memory. Asia-Pacific Psychiatry 2018;e12333
  22. Soni, S., Muthukrishnan, S. P., Sood, M., Kaur, S., & Sharma, R. (2018). Hyperactivation of left inferior parietal lobule and left temporal gyri shortens resting EEG microstate in schizophrenia. Schizophrenia Research, 2018: 201, 204–207.
  23. Srivastava A, Goyal V, Sood SK, Sharma R.  Reduced saccadic velocity and pupillary width in young onset Parkinson’s disease Neurology, Psychiatry and Brain Research, 2018, 27: 17-20.
  24. Sharma S, Kaur S, Tripathi M, Talwar A, Sharma R. Differential Deficits in Attention, Working and Semantic Memory discriminates between Mild Cognitive Impairment and Alzheimer’s disease. Indian J of Physiology and Pharmacology. 2017: 61(4): 348-356.
  25. Muthukrishnan S-P, Gurja J-P, Sharma R. Does Heart Rate Variability Predict Human Cognitive Performance at Higher Memory Loads? Indian Journal of Physiology & Pharmacology. 2017; 61(1): 14-22
  26. Muthukrishnan S-P, Ahuja N, Mehta N, Sharma R. Functional brain microstate predicts the outcome in a visuospatial working memory task. Behavioural Brain Research. 2016, 314:134–42.
  27. Suriya-Prakash M, John-Preetham G, Sharma R. (2015) Is heart rate variability related to cognitive performance in visuospatial working memory? PeerJ PrePrints 3:e1377v1.
  28. Singh, Y., & Sharma, R. (2015). Individual Alpha Frequency (IAF) Based Quantitative EEG Correlates of Psychological Stress. Indian Journal of Physiology and Pharmacology59(4), 414–421.
  29. Yogesh Singh, Jayvardhan Singh, Ratna Sharma, Anjana Talwar. FFT transformed quantitative EEG analysis of short term memory load. Annals of Neuroscience, 22(3): 28-31, 2015
  30. Muthukrishnan Suriya-Prakash, Sharma R. A Novel Visuospatial Working Memory Task to Explore the Effect of Memory Load and Performance, International Journal of Brain and Cognitive Sciences, 4(1): 3-7, 2015.
  31. Suneetha Sampath, S.C. Mahapatra, M.M. Padhi, Ratna Sharma and Anjana Talwar. Holy basil (Ocimum sanctum Linn.) leaf extract enhances specific cognitive parameters in healthy adult volunteers: A placebo controlled study Indian J Physiol Pharmacol 2015; 59(1): 69-77.
  32. Anshul Srivastava; Ratna Sharma, Sanjay Kumar Sood, Garima Shukla, Vinay Goyal, Madhuri Behari . Saccadic Eye Movements in Parkinson’s disease. Indian Journal of Opthalamology, Vol. 62(5): 538-544, 2014.
  33. Anshul Srivastava, Vinay Goyal, Sanjay Kumar Sood, Ratna Sharma.  Cognition and control of saccadic system. P. Gamito, & P. Rosa (Eds.). I see you, you see me: Inferring cognitive and emotional processes from gazing behaviour. Newcastle-upon-Tyne: Cambridge Scholars Publishing. ISBN (13): 978-1-4438-5460-3, 2014.
  34. Singh Y, Sharma R, Relationship between General Intelligence, Emotional Intelligence, Stress Levels and Stress Reactivity. Annals of Neuroscience, 19(3):107-111, 2012.
  35. Singh Y, Sharma R, Talwar A. Immediate and long term effects of Meditation on acute stress reactivity, cognitive functions and intelligence, Alternative Therapies in Health and Medicine, 18 (6): 46-52, 2012
  36. Yadav RK, Magan D, Mehta N, Sharma R, Mahapatra SC. Efficacy of a Short-term Yoga-based Lifestyle Intervention in Reducing Stress and Inflammation: Preliminary Results" J Altern Complement Med. 2012 Jul;18(7):662-7.
  37. Mohan A, Sharma R, Bijlani RL, Effect of Meditation on Stress-Induced Changes in Cognitive Functions. J Compl Alt Med, 17(3): 207-212, 2011.
  38. Sharma R, Gupta N, Bijlani RL Effect of yoga based lifestyle intervention on subjective well being. Ind J Physiol Pharmacol, 52(2): 123-131, 2008.
  39. Sharma R, Khera, S, Mohan A, Gupta, N, Basu Ray, Assessment of computer game as a psychological stressor. Ind J Physiol Pharmacol, 50(4): 367-374, 2006.
  40. Sharma R, Meditation and mental well being. Ind J Physiol Pharmacol, 50(3):  205-214, 2006.
  41. Meena NB, Jain S, Sharma R, Mathur R, and Nayar U Amygdalar neuronal responses to peripheral noxious stimuli in rats. Ind J Physiol Pharmacol, 50(1): 17-27, 2006. 
  42. Gupta N, Khera, S, Vempati, RP, Sharma R, Bijlani RL Effect of yoga based lifestyle intervention on state and trait anxiety. Ind J Physiol Pharmacol, 50(1): 41-47, 2006. 
  43. Bijlani R L, Vempati R P, Yadav R K, Basu Ray R, Gupta V, Sharma R, Mehta N, Mahapatra S C A brief but comprehensive lifestyle education programme based on Yoga reduces risk factors for cardiovascular disease and diabetes mellitus. J Compl Alt Med, 11(2): 267–274, 2005.
  44. Jain S, Sharma R, Wadhawa S, Effect of prenatal species-specific and music stimulation on the postnatal auditory preference of domestic chick. Ind J Physiol Pharmacol, 48(2):174-183, 2004.
  45. Jain S, Mathur R, Sharma R, Nayar U, Recovery from lesion associated learning deficits by fetal amygdala transplantation. Neural Plasticity, 9:53-63, 2001.
  46. Jain S, Sharma R, Analgesia in the tonic and phasic pain tests in a pharmacological model of autotomy. Indian J exptl biol, 40:1269-1274, 2002.
  47. Jain S, Mathur R, Sharma R and Nayar U, Reversal of hyperalgesia by transplantation in lateral hypothalamic lesioned rats. Neurobiology, 9(1):17-22, 2001.
  48. Jain S, Mathur R, Sharma R and Nayar U Effect of tonic pain on schedule specific feeding behaviour. Indian Journal of Experimental Biology, 38:834-836, 2000.
  49. Jain S, Mathur R, Sharma R and Nayar U, Foetal amygdalar transplantation facilitates recovery of retention deficit in CeA lesioned rats. Indian Journal of Experimental Biology, 38:1014-1019, 2000.
  50. Jain S, Mathur R, Sharma R and Nayar U, Neural tissue transplant in the lateral hypothalamic lesioned rats: Functional recovery pattern. Neurobiology, 7(4): 2000.
  51. Jain S, Mathur R, Sharma R and Nayar U, Amygdalar tissue transplants improve recovery of the nociceptive behaviour. Restorative Neurology and  Neuroscience, 16(2): 1-5, 2000.
  52. Sharma R, Sinha R, Mathur R, and Nayar U, Neuronal responses of periaqeductal gray to peripheral noxious stimulation. Ind J Physiol Pharmacol, 43(4): 449-457, 1999.
  53. Sinha R, Sharma R, Mathur R, and Nayar U, Hypothalamo-Limbic involvement in modulation of tooth-pulp stimulation evoked nociceptive response in rats. Ind J Physiol Pharmacol,  43(3): 323-331, 1999.
  54. Sharma R, Mathur R, and Nayar U, GABA B mediated analgesia in tonic pain in monkeys. Ind J Physiol Pharmacol, 37(1), 1993.
  55. Mohan Kumar V, Sharma R, Wadhawa S and Manchanda  SK, Sleep  inducing function of noradrenergic fibres in  the medial preoptic area.  Brain Research Bulletin, 32(2): 153-158, 1993.
  56. Sharma R, Manchanda SK and Nayar U,   Role of opioid receptors   in self aggression in rats.   Ind J   Physiol Pharmacol, 35(3):165-169, 1991.


Chapters in Books
  1. Nayar U, Sharma R, Sinha R, Narasaiah M and Mathur R Endogenous pain control, mechanisms In : Current trends in pain research and therapy-Advances in pain research and therapy Eds GP Dureja and TS Jayalakshmi 199, pp-9-16.
  2. Sharma R Yoga and pain relief In: Emerging concepts in yoga and lifestyle Eds: Neena Bhatacharya, B H Paudel 2004, pp55-60.
  3. A Srivastava, V Goyal, SK Sood, R Sharma. Cognition and control of saccadic system. In  P. Gamito (Eds) “I see me, you see me: inferring cognitive and emotional processes from gazing behavior”.Cambridge Scholars Publishing. (Accepted for publication).

Letter to editor

  1. Kaur S, Sharma R, Rastogi S. "Demystifying the Association of Chemotherapy and Cognition: How Close Are We?" Journal of Clinical Oncology, 34(30), pp. 3707–3708, 2016.
  2. Leon C, Sharma R, Kaur S. Attention-deficit/hyperactive disorder: missing the bull’s eye Evid Based Mental Health Epub ahead of print: doi:10.1136/ebmental-2018-300079.Evid Based Mental Health 2019;0. doi:10.1136/ ebmental-2018-300079


Research Projects as Chief Investigator:-  

  1. Microstate signatures and resting EEG sources of meditation and stress, DST, Sanctioned in 2020
  2. EEG microstates that favor perceptual reversal of emotional stimuli compared to perceptual stability in schizophrenia during binocular rivalry, STS project, ICMR 2020
  3. QEEG correlates of Default Mode Network activity and its correlation with cognitive deficits in Multiple System Atrophy-Parkinsonian type and Multiple system Atrophy -Cerebellar Ataxia type” ICMR RA, 2019-2022
  4. EEG microstate and phase coherence correlates of cognitive deficits in Parkinson’s disease, ICMR, SRF, 2016-2019
  5. A study of EEG microstates and source connectivity as state and trait markers in schizophrenia with depression, ICMR RA, 2019-2022
  6. Blood heavy metal levels and quantitative EEG correlates in children with autism, 2014-2019: ICMR in collaboration with Pediatric Neurology
  7. Quantitative EEG correlates of Cognitive deficits in Parkinson Disease, DBT, 2011-2014, Rs 22 lakhs
  8. A study of quantitative EEG changes, cognitive function and stress in mild cognitive impairment and Alzheimer’s disease, DST, 2010-2013, Rs 82 lakhs
  9. Cognition induced changes in brain oscillations, IRG, 2009-2010, Rs 2 lakhs
  10. A study on stress reactivity of students as a function of their general and emotional intelligence and effect of meditation on the stress response, IRG, 2007-2009, Rs 1.4 lakhs
  11. A study to assess acute mental stress induced changes in EEG, cognitive behavior and neurosteroids across the menstrual cycle and effect of meditation on stress induced changes, CCRYN, Ministry of Health, 2006-2009, Rs 15 lakhs
  12. The effect of stress induced changes in theta and alpha bands during memory retrieval. IRG, 2005-2007, Rs 1.4 lakhs
  13. A randomized controlled trial on the efficacy of yogic intervention in premenstrual syndrome, ICMR, 2003-2006, Rs 16 lakhs
  14. Effect of prenatal auditory overstimulation with species-specific music sounds on postnatal learning in domestic chicks, IRG, 2003-2005, Rs 80,000
  15. Effect of meditation on Stress induced changes in cognitive functions. IRG, 2002-2003 Rs 30,000
  16. Pain mechanisms in autotomy: deafferentation vs pharmacological model. IRG, 2000-200, Rs 25,000
  17. Pain mechanisms in autotomy, IRG, 1998-1999, Rs 25,000
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